Sort of squash (5)
I believe the answer is:
acorn
'sort of squash' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for acorn that I've seen before include "Potentially future tree" , "Source of a great oak" , "Dirt on a liquid surface" , "oak's fruit" , "Fruit of the oak tree" .)